Test execution time analysis in JUnit - Build an Automation Script

Measure and verify test execution time for a sample method

Preconditions (2)

Step 1: Create a test method for the sample method

Step 2: Record the start time before calling the sample method

Step 3: Call the sample method

Step 4: Record the end time after the method call

Step 5: Calculate the elapsed time by subtracting start time from end time

Step 6: Assert that the elapsed time is less than or equal to 1000 milliseconds

✅ Expected Result: The test passes if the sample method executes within 1000 milliseconds, otherwise it fails

Automation Requirements - JUnit 5

Assertions Needed:

Assert that the execution time is less than or equal to 1000 milliseconds

Best Practices:

Use System.nanoTime() for precise time measurement

Use assertions from org.junit.jupiter.api.Assertions

Keep test methods small and focused

Avoid hardcoded sleep or waits in tests

Use descriptive test method names

Automated Solution

JUnit

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class ExecutionTimeTest {

    // Sample method to test
    public void sampleMethod() {
        // Simulate some work by sleeping for 500 milliseconds
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }

    @Test
    public void testSampleMethodExecutionTime() {
        long startTime = System.nanoTime();
        sampleMethod();
        long endTime = System.nanoTime();

        long durationInMillis = (endTime - startTime) / 1_000_000;

        assertTrue(durationInMillis <= 1000, "Execution time should be less than or equal to 1000 ms but was " + durationInMillis + " ms");
    }
}

This test measures how long sampleMethod() takes to run.

We use System.nanoTime() before and after the method call to get precise timing.

The difference is converted to milliseconds.

We then assert the duration is less than or equal to 1000 ms.

If the method runs longer, the test fails with a clear message.

This helps ensure performance expectations are met.

Common Mistakes - 4 Pitfalls

Using System.currentTimeMillis() instead of System.nanoTime()

Hardcoding Thread.sleep() in tests to simulate delays

Not converting nanoseconds to milliseconds for assertion

Not providing a clear assertion message

Bonus Challenge

Now add data-driven testing to measure execution time for three different sample methods with varying sleep durations (200ms, 500ms, 800ms).

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